1. Field of the Invention
The present invention generally relates to an auger-type ice making machine. More particularly, the invention is concerned with an improvement of an auger-type ice making machine such that protection can be secured for a driving motor and other components upon occurrence of jamming of ice or the like obstructive phenomenon within a refrigerating cylinder of the ice making machine while providing measures for speedily clearing away such unwanted phenomena without fail.
2. Description of the Related Art
In a so-called auger-type ice making machine, raw water (i.e., water used for manufacturing ice) is fed into a refrigerating cylinder around which a coolant vaporizing tube communicated to a refrigerating circuit is wound, wherein an ice layer grown on an inner wall surface of the refrigerating cylinder is scraped off by a spiral blade extending spirally around an auger which serves for transporting ice thus detached upwardly to an exit or outlet port as well. Because of capability of manufacturing flake-like ice chips as well as ice pellets or cubes formed by compressing the ice chips, the auger-type ice making machine is widely used.
In this type ice making machine, a press head assembly is installed at an outlet provided at a top end of the refrigerating cylinder in order to dewater and solidify the ice chips under pressure. Consequently, jamming of ice may occur within the press head assembly and the refrigerating cylinder for a variety of causes. When such an ice jamming phenomenon takes place, the cylinder is subjected to an excessively large load, which may often result in burning or the like damage of an auger driving motor such as a geared motor. As the measures for coping with this problem, there is proposed a technique according to which lowering of a pressure for coolant vaporization due to the ice jamming is detected, whereupon a high-temperature gas (also referred to as hot gas) is fed into the coolant vaporizing tube to thereby melt or fuse the clogging ice, as is disclosed, for example, in Japanese Patent Publication No. 56-40259.
Although the above-mentioned technique of melting the ice clogging by resorting to the use of hot gas can certainly assure desired effects to some extent, it suffers from another problem that a lot of time is taken for clearing away the ice clogging because heat of the hot gas is transmitted to the inner wall surface of the refrigerating cylinder to thereby cause a cavity to be formed along the cylinder inner surface because of absence of the coolant vaporizing tube around the press head assembly. Besides, additional provision of the hot gas pipe involves complication in the structure, to another disadvantage.
As an approach tackling the problems mentioned above, there is proposed, for example, in Japanese Patent Publication No. 3-32716 a technique for melting away the ice clogging by supplying continuously raw water from a feed water system or circuit. This prior art method will be elucidated by reference to FIGS. 12 and 13 of the accompanying drawings.
Referring to FIG. 12, a coolant of high pressure discharged from a compressor 1 is condensed within a condenser 3 which is cooled by a fan 2 and vaporized within a vaporizing tube 4 to thereby cool a refrigerating cylinder 5 by depriving of heat. An auger 6 mounted within the refrigerating cylinder 5 is rotatively driven by a geared motor 8 through a reduction gear 7 to thereby scrape off ice formed on the inner wall surface of the refrigerating cylinder 5. The ice chips thus formed are fed into a discharge cylinder 10 through a compressing passage formed in a press head assembly 9. For supplying raw water to the refrigerating cylinder 5, water is tapped from a water service via a pipe 12 having a feed valve 11 installed therein to be first supplied to a feed water tank 13, from which water is fed into the refrigerating cylinder 5 via a feed pipe 14. On the other hand, water is drained through a drain pipe 16 equipped with a drain valve 15. Control of water level within the refrigerating cylinder 5 is effected by controlling correspondingly the feed valve 11 by means of a float switch 17 disposed within the feed water tank 16.
The auger-type ice making machine of the structure described above is provided with an electric circuit shown in FIG. 13. In operation, when a main switch S is closed, the feed valve 11 is opened under the actions of the float switch 17 and relays R1 and R2, whereby water is supplied to the feed water tank 13 until the water level therein attains a predetermined height. Upon completion of the feed water supply, ice making operation is started by supplying electric energy to the compressor 1, the motor-driven fan unit 2 and the geared motor 8 so long as the ice making machine can operate normally. When jamming of ice takes place, excessive cooling is detected by a thermostat 18 or alternatively overload of the geared motor 8 is detected by an overcurrent detector 19. Then, the drain valve 15 is opened, whereby water resident within the refrigerating cylinder 5 is discharged or drained. As a result of this, the water level within the feed water tank 13 is lowered to cause the float switch 17 to be actuated. Thus, water is fed into the water tank 13. In this way, feeding and draining of water are performed simultaneously, whereby raw water is caused to flow into the refrigerating cylinder and flow out therefrom. Under the effect of sensible heat of the feed water, ice is molten, whereby the jamming or clogging is cleared away. Before a time preset in a timer TM has lapsed, the ice making operation is not restarted even when the thermostat is restored to the normal state. Thus, the feed water continues to flow through the refrigerating cylinder in vain.
The continuous water feeding and draining mentioned above present a problem remaining to be solved. Namely, the ice jamming or clogging generally takes place initially in a tom end portion of the refrigerating cylinder and propagates downwardly. By contrast, the feed pipe and the drain pipe are communicated to the refrigerating cylinder at a lower portion thereof. Consequently, water as fed tends to flow primarily through a bottom end portion of the refrigerating cylinder. Thus, the ice melting action of feed water can become effective only with a considerable time lag. As a result, a lot of time is required for melting away the ice clogging. Besides, a remarkably large amount of fresh water will be consumed. Such unfavorable phenomenon becomes significant in the winter season where temperature of feed water is low.
When the time preset in the timer TM has lapsed with the thermostat 18 being restored to the normal state as the ice melting process proceeds normally, the ice making operation is automatically restarted. Thus, maintenance for operation of the auger-type ice making machine can be facilitated. However, unless the fundamental measures for removing the causes of the ice jamming phenomenon are taken, the overload/overcurrent event of the geared motor due to the ice jamming will occur repetitively, incurring possibly more serious failure or accident.